2 % (c) The AQUA Project, Glasgow University, 1998
4 \section[DsCCall]{Desugaring \tr{foreign} declarations}
6 Expanding out @foreign import@ and @foreign export@ declarations.
9 module DsForeign ( dsForeigns ) where
11 #include "HsVersions.h"
15 import DsCCall ( dsCCall, mkFCall, boxResult, unboxArg, resultWrapper )
18 import HsSyn ( ForeignDecl(..), ForeignExport(..),
19 ForeignImport(..), CImportSpec(..) )
20 import TcHsSyn ( TypecheckedForeignDecl )
21 import CoreUtils ( exprType, mkInlineMe )
22 import Id ( Id, idType, idName, mkVanillaGlobal, mkSysLocal,
24 import IdInfo ( vanillaIdInfo )
25 import Literal ( Literal(..) )
26 import Module ( Module, moduleUserString )
27 import Name ( mkGlobalName, nameModule, nameOccName, getOccString,
28 mkForeignExportOcc, isLocalName,
31 import Type ( repType, eqType )
32 import TcType ( Type, mkFunTys, mkForAllTys, mkTyConApp,
34 tcSplitForAllTys, tcSplitFunTys, tcTyConAppArgs,
35 tcSplitTyConApp_maybe, tcSplitAppTy,
39 import ForeignCall ( ForeignCall(..), CCallSpec(..),
42 CCallConv(..), ccallConvToInt,
45 import CStrings ( CLabelString )
46 import TysWiredIn ( addrTy, unitTy, stablePtrTyCon )
47 import TysPrim ( addrPrimTy )
48 import PrelNames ( hasKey, ioTyConKey, deRefStablePtrName, newStablePtrName,
49 bindIOName, returnIOName
51 import BasicTypes ( Activation( NeverActive ) )
52 import ErrUtils ( addShortWarnLocLine )
54 import Maybe ( fromJust )
57 Desugaring of @foreign@ declarations is naturally split up into
58 parts, an @import@ and an @export@ part. A @foreign import@
61 foreign import cc nm f :: prim_args -> IO prim_res
65 f :: prim_args -> IO prim_res
66 f a1 ... an = _ccall_ nm cc a1 ... an
68 so we reuse the desugaring code in @DsCCall@ to deal with these.
71 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
72 -- the occurrence analyser will sort it all out
75 -> [TypecheckedForeignDecl]
76 -> DsM ( [Id] -- Foreign-exported binders;
77 -- we have to generate code to register these
79 , SDoc -- Header file prototypes for
80 -- "foreign exported" functions.
81 , SDoc -- C stubs to use when calling
82 -- "foreign exported" functions.
83 , [FAST_STRING] -- headers that need to be included
84 -- into C code generated for this module
86 dsForeigns mod_name fos
87 = foldlDs combine ([], [], empty, empty, []) fos
89 combine (acc_feb, acc_f, acc_h, acc_c, acc_header)
90 (ForeignImport id _ spec depr loc)
91 = dsFImport mod_name id spec `thenDs` \(bs, h, c, hd) ->
92 warnDepr depr loc `thenDs` \_ ->
93 returnDs (acc_feb, bs ++ acc_f, h $$ acc_h, c $$ acc_c, hd ++ acc_header)
95 combine (acc_feb, acc_f, acc_h, acc_c, acc_header)
96 (ForeignExport id _ (CExport (CExportStatic ext_nm cconv)) depr loc)
97 = dsFExport mod_name id (idType id)
98 ext_nm cconv False `thenDs` \(feb, b, h, c) ->
99 warnDepr depr loc `thenDs` \_ ->
100 returnDs (feb:acc_feb, b : acc_f, h $$ acc_h, c $$ acc_c, acc_header)
102 warnDepr False _ = returnDs ()
103 warnDepr True loc = dsWarn (addShortWarnLocLine loc msg)
105 msg = ptext SLIT("foreign declaration uses deprecated non-standard syntax")
109 %************************************************************************
111 \subsection{Foreign import}
113 %************************************************************************
115 Desugaring foreign imports is just the matter of creating a binding
116 that on its RHS unboxes its arguments, performs the external call
117 (using the @CCallOp@ primop), before boxing the result up and returning it.
119 However, we create a worker/wrapper pair, thus:
121 foreign import f :: Int -> IO Int
123 f x = IO ( \s -> case x of { I# x# ->
124 case fw s x# of { (# s1, y# #) ->
127 fw s x# = ccall f s x#
129 The strictness/CPR analyser won't do this automatically because it doesn't look
130 inside returned tuples; but inlining this wrapper is a Really Good Idea
131 because it exposes the boxing to the call site.
137 -> DsM ([Binding], SDoc, SDoc, [FAST_STRING])
138 dsFImport modName id (CImport cconv safety header lib spec)
139 = dsCImport modName id spec cconv safety `thenDs` \(ids, h, c) ->
140 returnDs (ids, h, c, if _NULL_ header then [] else [header])
141 -- FIXME: the `lib' field is needed for .NET ILX generation when invoking
142 -- routines that are external to the .NET runtime, but GHC doesn't
143 -- support such calls yet; if `_NULL_ lib', the value was not given
144 dsFImport modName id (DNImport spec)
145 = dsFCall modName id (DNCall spec) `thenDs` \(ids, h, c) ->
146 returnDs (ids, h, c, [])
153 -> DsM ([Binding], SDoc, SDoc)
154 dsCImport modName id (CLabel cid) _ _
155 = ASSERT(fromJust resTy `eqType` addrPrimTy) -- typechecker ensures this
156 returnDs ([(id, rhs)], empty, empty)
158 (resTy, foRhs) = resultWrapper (idType id)
159 rhs = foRhs (mkLit (MachLabel cid))
160 dsCImport modName id (CFunction target) cconv safety
161 = dsFCall modName id (CCall (CCallSpec target cconv safety))
162 dsCImport modName id CWrapper cconv _
163 = dsFExportDynamic modName id cconv
167 %************************************************************************
169 \subsection{Foreign calls}
171 %************************************************************************
174 dsFCall mod_Name fn_id fcall
177 (tvs, fun_ty) = tcSplitForAllTys ty
178 (arg_tys, io_res_ty) = tcSplitFunTys fun_ty
179 -- Must use tcSplit* functions because we want to
180 -- see that (IO t) in the corner
182 newSysLocalsDs arg_tys `thenDs` \ args ->
183 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
186 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
188 -- These are the ids we pass to boxResult, which are used to decide
189 -- whether to touch# an argument after the call (used to keep
190 -- ForeignObj#s live across a 'safe' foreign import).
191 maybe_arg_ids | unsafe_call fcall = work_arg_ids
194 boxResult maybe_arg_ids io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
196 getUniqueDs `thenDs` \ ccall_uniq ->
197 getUniqueDs `thenDs` \ work_uniq ->
200 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
201 the_ccall_app = mkFCall ccall_uniq fcall val_args ccall_result_ty
202 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
203 work_id = mkSysLocal SLIT("$wccall") work_uniq worker_ty
206 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
207 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
208 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
210 returnDs ([(work_id, work_rhs), (fn_id, wrap_rhs)], empty, empty)
212 unsafe_call (CCall (CCallSpec _ _ safety)) = playSafe safety
213 unsafe_call (DNCall _) = False
217 %************************************************************************
219 \subsection{Foreign export}
221 %************************************************************************
223 The function that does most of the work for `@foreign export@' declarations.
224 (see below for the boilerplate code a `@foreign export@' declaration expands
227 For each `@foreign export foo@' in a module M we generate:
229 \item a C function `@foo@', which calls
230 \item a Haskell stub `@M.$ffoo@', which calls
232 the user-written Haskell function `@M.foo@'.
236 -> Id -- Either the exported Id,
237 -- or the foreign-export-dynamic constructor
238 -> Type -- The type of the thing callable from C
239 -> CLabelString -- The name to export to C land
241 -> Bool -- True => foreign export dynamic
242 -- so invoke IO action that's hanging off
243 -- the first argument's stable pointer
244 -> DsM ( Id -- The foreign-exported Id
249 dsFExport mod_name fn_id ty ext_name cconv isDyn
250 = -- BUILD THE returnIO WRAPPER, if necessary
251 -- Look at the result type of the exported function, orig_res_ty
252 -- If it's IO t, return (\x.x, IO t, t)
253 -- If it's plain t, return (\x.returnIO x, IO t, t)
254 (case tcSplitTyConApp_maybe orig_res_ty of
255 -- We must use tcSplit here so that we see the (IO t) in
256 -- the type. [IO t is transparent to plain splitTyConApp.]
258 Just (ioTyCon, [res_ty])
259 -> ASSERT( ioTyCon `hasKey` ioTyConKey )
260 -- The function already returns IO t
261 returnDs (\body -> body, orig_res_ty, res_ty)
263 other -> -- The function returns t, so wrap the call in returnIO
264 dsLookupGlobalValue returnIOName `thenDs` \ retIOId ->
265 returnDs (\body -> mkApps (Var retIOId) [Type orig_res_ty, body],
266 tcFunResultTy (applyTy (idType retIOId) orig_res_ty),
267 -- We don't have ioTyCon conveniently to hand
270 ) `thenDs` \ (return_io_wrapper, -- Either identity or returnIO
275 -- BUILD THE deRefStablePtr WRAPPER, if necessary
277 newSysLocalDs stbl_ptr_ty `thenDs` \ stbl_ptr ->
278 newSysLocalDs stbl_ptr_to_ty `thenDs` \ stbl_value ->
279 dsLookupGlobalValue deRefStablePtrName `thenDs` \ deRefStablePtrId ->
280 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
282 the_deref_app = mkApps (Var deRefStablePtrId)
283 [ Type stbl_ptr_to_ty, Var stbl_ptr ]
285 stbl_app cont = mkApps (Var bindIOId)
286 [ Type stbl_ptr_to_ty
289 , mkLams [stbl_value] cont]
291 returnDs (stbl_value, stbl_app, stbl_ptr)
295 panic "stbl_ptr" -- should never be touched.
296 )) `thenDs` \ (i, getFun_wrapper, stbl_ptr) ->
300 getModuleDs `thenDs` \ mod ->
301 getUniqueDs `thenDs` \ uniq ->
302 getSrcLocDs `thenDs` \ src_loc ->
303 newSysLocalsDs fe_arg_tys `thenDs` \ fe_args ->
305 wrapper_args | isDyn = stbl_ptr:fe_args
306 | otherwise = fe_args
308 wrapper_arg_tys | isDyn = stbl_ptr_ty:fe_arg_tys
309 | otherwise = fe_arg_tys
311 helper_ty = mkForAllTys tvs $
312 mkFunTys wrapper_arg_tys io_res_ty
314 f_helper_glob = mkVanillaGlobal helper_name helper_ty vanillaIdInfo
318 | isLocalName name = mod_name
319 | otherwise = nameModule name
321 occ = mkForeignExportOcc (nameOccName name)
322 helper_name = mkGlobalName uniq mod occ src_loc
324 the_app = getFun_wrapper (return_io_wrapper (mkVarApps (Var i) (tvs ++ fe_args)))
325 the_body = mkLams (tvs ++ wrapper_args) the_app
327 (h_stub, c_stub) = fexportEntry (moduleUserString mod)
328 ext_name f_helper_glob
329 wrapper_arg_tys res_ty cconv isDyn
331 returnDs (f_helper_glob, (f_helper_glob, the_body), h_stub, c_stub)
334 (tvs,sans_foralls) = tcSplitForAllTys ty
335 (fe_arg_tys', orig_res_ty) = tcSplitFunTys sans_foralls
336 -- We must use tcSplits here, because we want to see
337 -- the (IO t) in the corner of the type!
339 fe_arg_tys | isDyn = tail fe_arg_tys'
340 | otherwise = fe_arg_tys'
342 stbl_ptr_ty | isDyn = head fe_arg_tys'
343 | otherwise = error "stbl_ptr_ty"
345 (_, stbl_ptr_ty') = tcSplitForAllTys stbl_ptr_ty
346 (_, stbl_ptr_to_ty) = tcSplitAppTy stbl_ptr_ty'
347 -- Again, stable pointers are just newtypes,
348 -- so we must see them! Hence tcSplit*
351 @foreign export dynamic@ lets you dress up Haskell IO actions
352 of some fixed type behind an externally callable interface (i.e.,
353 as a C function pointer). Useful for callbacks and stuff.
356 foreign export dynamic f :: (Addr -> Int -> IO Int) -> IO Addr
358 -- Haskell-visible constructor, which is generated from the above:
359 -- SUP: No check for NULL from createAdjustor anymore???
361 f :: (Addr -> Int -> IO Int) -> IO Addr
363 bindIO (newStablePtr cback)
364 (\StablePtr sp# -> IO (\s1# ->
365 case _ccall_ createAdjustor cconv sp# ``f_helper'' s1# of
366 (# s2#, a# #) -> (# s2#, A# a# #)))
368 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
369 -- `special' foreign export that invokes the closure pointed to by the
374 dsFExportDynamic :: Module
377 -> DsM ([Binding], SDoc, SDoc)
378 dsFExportDynamic mod_name id cconv
379 = newSysLocalDs ty `thenDs` \ fe_id ->
381 -- hack: need to get at the name of the C stub we're about to generate.
382 fe_nm = _PK_ (moduleUserString mod_name ++ "_" ++ toCName fe_id)
384 dsFExport mod_name id export_ty fe_nm cconv True `thenDs` \ (feb, fe, h_code, c_code) ->
385 newSysLocalDs arg_ty `thenDs` \ cback ->
386 dsLookupGlobalValue newStablePtrName `thenDs` \ newStablePtrId ->
388 mk_stbl_ptr_app = mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
390 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
391 newSysLocalDs (mkTyConApp stablePtrTyCon [arg_ty]) `thenDs` \ stbl_value ->
394 = mkApps (Var bindIOId)
395 [ Type (mkTyConApp stablePtrTyCon [arg_ty])
402 The arguments to the external function which will
403 create a little bit of (template) code on the fly
404 for allowing the (stable pointed) Haskell closure
405 to be entered using an external calling convention
408 adj_args = [ mkIntLitInt (ccallConvToInt cconv)
410 , mkLit (MachLabel fe_nm)
412 -- name of external entry point providing these services.
413 -- (probably in the RTS.)
414 adjustor = SLIT("createAdjustor")
416 dsCCall adjustor adj_args PlayRisky False io_res_ty `thenDs` \ ccall_adj ->
417 -- PlayRisky: the adjustor doesn't allocate in the Haskell heap or do a callback
418 let ccall_adj_ty = exprType ccall_adj
419 ccall_io_adj = mkLams [stbl_value] $
420 Note (Coerce io_res_ty ccall_adj_ty)
422 io_app = mkLams tvs $
424 stbl_app ccall_io_adj res_ty
425 fed = (id `setInlinePragma` NeverActive, io_app)
426 -- Never inline the f.e.d. function, because the litlit
427 -- might not be in scope in other modules.
429 returnDs ([fed, fe], h_code, c_code)
433 (tvs,sans_foralls) = tcSplitForAllTys ty
434 ([arg_ty], io_res_ty) = tcSplitFunTys sans_foralls
435 [res_ty] = tcTyConAppArgs io_res_ty
436 -- Must use tcSplit* to see the (IO t), which is a newtype
437 export_ty = mkFunTy (mkTyConApp stablePtrTyCon [arg_ty]) arg_ty
439 toCName :: Id -> String
440 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
445 \subsection{Generating @foreign export@ stubs}
449 For each @foreign export@ function, a C stub function is generated.
450 The C stub constructs the application of the exported Haskell function
451 using the hugs/ghc rts invocation API.
454 fexportEntry :: String
462 fexportEntry mod_nm c_nm helper args res_ty cc isDyn = (header_bits, c_bits)
464 -- name of the (Haskell) helper function generated by the desugarer.
465 h_nm = ppr helper <> text "_closure"
466 -- prototype for the exported function.
467 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
469 fun_proto = cResType <+> pprCconv <+> ptext c_nm <>
470 parens (hsep (punctuate comma (zipWith (<+>) cParamTypes proto_args)))
476 , text "SchedulerStatus rc;"
478 -- create the application + perform it.
479 , text "rc=rts_evalIO"
480 <> parens (foldl appArg (text "(StgClosure*)deRefStablePtr(a0)")
481 (tail (zip args c_args))
486 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ptext c_nm)
487 <> comma <> text "rc") <> semi
488 , text "return" <> return_what <> semi
493 text "rts_apply" <> parens (acc <> comma <> mkHObj a <> parens c_a)
495 cParamTypes = map showStgType real_args
497 res_ty_is_unit = res_ty `eqType` unitTy -- Look through any newtypes
499 cResType | res_ty_is_unit = text "void"
500 | otherwise = showStgType res_ty
502 pprCconv = case cc of
504 StdCallConv -> text (ccallConvAttribute cc)
506 declareResult = text "HaskellObj ret;"
508 mkExtern ty nm = text "extern" <+> ty <+> nm <> semi
510 return_what | res_ty_is_unit = empty
511 | otherwise = parens (unpackHObj res_ty <> parens (text "ret"))
513 c_args = mkCArgNames 0 args
516 If we're generating an entry point for a 'foreign export ccall dynamic',
517 then we receive the return address of the C function that wants to
518 invoke a Haskell function as any other C function, as second arg.
519 This arg is unused within the body of the generated C stub, but
520 needed by the Adjustor.c code to get the stack cleanup right.
522 (proto_args, real_args)
524 CCallConv | isDyn -> ( text "a0" : text "original_return_addr"
525 : mkCArgNames 1 (tail args)
526 , head args : addrTy : tail args)
527 other -> (mkCArgNames 0 args, args)
529 mkCArgNames :: Int -> [a] -> [SDoc]
530 mkCArgNames n as = zipWith (\ _ n -> text ('a':show n)) as [n..]
532 mkHObj :: Type -> SDoc
533 mkHObj t = text "rts_mk" <> text (showFFIType t)
535 unpackHObj :: Type -> SDoc
536 unpackHObj t = text "rts_get" <> text (showFFIType t)
538 showStgType :: Type -> SDoc
539 showStgType t = text "Hs" <> text (showFFIType t)
541 showFFIType :: Type -> String
542 showFFIType t = getOccString (getName tc)
544 tc = case tcSplitTyConApp_maybe (repType t) of
546 Nothing -> pprPanic "showFFIType" (ppr t)